The objective of this proposal is to accelerate the identification of zebrafish genes discovered during mutagenesis screens. This proposal is in response to PAR-02-142 to develop "Tools for Genetic Studies in Zebrafish." A major focus of this PA is to use novel screens to identify mutants of interest. However, an essential part of this effort is to identify the genes responsible for the novel phenotypes generated. While thousands of mutants already have been described, only 167 genes are listed in the zebrafish database (ZFIN) for which mutations are known (although there are probably some not listed). The major reason for this is the time consuming nature of the positional cloning strategy that must be used. The major bottleneck in gene discovery by positional cloning is the need to do whole genome linkage mapping. This takes considerable resources and time, as well as technical expertise. This goal of this proposal is to eliminate this bottleneck by setting up a high throughput mapping facility. The usual laborious task of screening sometimes hundreds of markers to find one that is linked to the mutation of interest will be accomplished in 2 days. This will be done using fluorescence sequencers to automate genotyping of SSLPs (short sequence length polymorphisms) that span the genome. The mapping will be done in two main stages. First, an approximate location will be determined using bulk segregant analyses. Second, once closely flanking markers are identified 500-1000 individual mutant embryos will be genotyped to identify the region containing the mutant gene. Third, for a small number of mutants the genes will be identified. The core will map a minimum of 100 mutants per year and identify the gene in 5-10, although both these numbers are likely to increase dramatically once the genome sequence is completed. The service will be modular so that investigators can have the initial mapping phases done by the facility, and then complete the mutant gene isolation in there own laboratories. This project will have considerable impact because it will greatly accelerate the discovery of genes that already have been shown to be models of human diseases. The facility is committed to full and open access and all data pertaining to mapping will be made available at publication. Given the importance of zebrafish as a model organism this facility will have an immediate impact on the rate at which mutant genes are discovered, which will provide new insights into the genetic underpinnings of important biochemical pathways involved in disease.